The collection contains three separate maps giving an overview of three declining phenomena of the dialectal phonology. Each map traces the phonological changes that took place in the 20th century from a different perspective: the map of Silesian assibilations in the second half of the 20th century from a synchronic perspective, the map of the Decline of the two kinds of l during the 20th century from a diachronic perspective, and the map of the Results of the evolution of the vowel y in the 20th century from a combined perspective. The maps are based on a number of published and unpublished sources and on calculations of a newly developed software tool, which was created in collaboration between dialectologists and geoinformaticians.